A pathological complete response after nivolumab plus ipilimumab therapy for DNA mismatch repair-deficient/microsatellite instability-high metastatic colon cancer: A case report

The standard treatment for colorectal cancer has always been surgery and chemotherapy, which may be used in combination to treat patients. Immune checkpoint inhibitors have been a significant advancement in the standard treatment of metastatic, unresectable colorectal cancer with deficient mismatch repair. However, little information is available about their use in neoadjuvant and conversion settings with only a few case reports and only one phase 2 trial. The present study reports the case of a large, locally advanced right-sided metastatic deficient mismatch repair/microsatellite instability-high colon cancer, which showed a pathological complete response after combination treatment with nivolumab and ipilimumab. To the best of our knowledge, resected metastatic colon cancer with a pathological complete response after treatment using dual immune checkpoint inhibitors has not been previously reported. Overall, this case report suggests the use of immune checkpoint inhibitors before colorectal surgery.     

MSS型结直肠癌免疫联合治疗研究进展

近年来,免疫治疗在恶性肿瘤治疗方面取得了很大的进展,已经丰富了多种恶性肿瘤的治疗模式。结直肠癌是全球三大常见的恶性肿瘤之一,免疫检查点抑制剂治疗对DNA错配修复缺陷（dMMR）/高微卫星不稳定性（MSI-H）转移性结直肠癌（mCRC）患者有显著临床获益,但约95%mCRC患者是错配修复完整（pMMR）/微卫星稳定（MSS）型,这类患者对单药免疫治疗的反应差,如何提高该类患者的免疫治疗疗效一直备受关注。本文就MSS型mCRC的免疫联合治疗研究进展进行综述。     

Mismatch repair deficient metastatic colon cancer and urothelial cancer: A case report of sequential immune checkpoint therapy

A major recent advance in cancer therapy involves the use of immune checkpoint therapy for tumors with mismatch repair deficiency, as they have a high tumor mutation load and neoantigen burden. Approximately 4% of advanced colorectal cancer harbors a mismatch repair deficiency. When mismatch repair deficiency exists in the germline, there is increased susceptibility to a variety of cancers including colorectal cancer, uterine cancer, urothelial carcinoma, and skin cancer. Herein we report the case of a 62-year-old man with mismatch repair deficient metastatic colorectal adenocarcinoma, urothelial carcinoma and a history of sebaceous carcinomas. As the patient in 2016 was ineligible for clinical trials he received immune checkpoint anti-PD-1 therapy with pembrolizumab (200 mg every 3 weeks), on compassionate use basis, after the failure of second-line treatment. The patient's CEA initially responded to pembrolizumab for 4 months and then kept rising for 5 months before mildly declining again. His treatment was then switched to anti-PD-L1 therapy with atezolizumab as it was approved for urothelial carcinoma at that time, and his CEA declined again. This case raises interesting questions about caring for patients with mismatch repair deficient colorectal cancer, including the role of PD-L1 therapy, sequencing of immunotherapy, relying on CEA trends and determining future therapies after progression on pembrolizumab.     

错配修复蛋白联合血清肿瘤标志物与Ki-67增殖指数对结直肠癌预后的临床价值

背景与目的：结直肠癌是消化系统常见的恶性肿瘤之一,近年来中国结直肠癌发病率显著升高。各项临床与病理学指标对于结直肠癌的诊断、临床分期及预后的判断提供了帮助。探讨错配修复蛋白表达联合血清肿瘤标志物与Ki-67增殖指数在结直肠癌中的相关性及对预后判断的临床价值。方法：收集复旦大学附属华东医院2014年7月—2018年6月收治的234例结直肠癌手术患者,分析其术前血清标本中肿瘤标志物癌胚抗原（carcinoembryonic antigen,CEA）、糖类抗原（carbohydrate antigen,CA）19-9、CA72-4、CA12-5水平及手术标本组织中的Ki-67增殖指数与错配修复蛋白的表达率,与结直肠癌临床病理学特征和预后的关系。结果：在234例结直肠癌患者术后标本中发生错配修复蛋白缺失表达（deficient mismatchrepair,dMMR）的共29例（12.4%）,错配修复蛋白正常表达（proficientmismatchrepair,pMMR）的有205例（87.6%）。在临床病理学指标的相关性分析中dMMR组与pMMR组在肿瘤原发部位、分化类型、分期、T分期、淋...     

Deficient mismatch repair system in patients with sporadic advanced colorectal cancer

A deficient mismatch repair system (dMMR) is present in 10–20% of patients with sporadic colorectal cancer (CRC) and is associated with a favourable prognosis in early stage disease. Data on patients with advanced disease are scarce. Our aim was to investigate the incidence and outcome of sporadic dMMR in advanced CRC. Data were collected from a phase III study in 820 advanced CRC patients. Expression of mismatch repair proteins was examined by immunohistochemistry. In addition microsatellite instability analysis was performed and the methylation status of the MLH1 promoter was assessed. We then correlated MMR status to clinical outcome. Deficient mismatch repair was found in only 18 (3.5%) out of 515 evaluable patients, of which 13 were caused by hypermethylation of the MLH1 promoter. The median overall survival in proficient MMR (pMMR), dMMR caused by hypermethylation of the MLH1 promoter and total dMMR was 17.9 months (95% confidence interval 16.2–18.8), 7.4 months (95% CI 3.7–16.9) and 10.2 months (95% CI 5.9–19.8), respectively. The disease control rate in pMMR and dMMR patients was 83% (95% CI 79–86%) and 56% (30–80%), respectively. We conclude that dMMR is rare in patients with sporadic advanced CRC. This supports the hypothesis that dMMR tumours have a reduced metastatic potential, as is observed in dMMR patients with early stage disease. The low incidence of dMMR does not allow drawing meaningful conclusions about the outcome of treatment in these patients.     

Mismatch repair polymorphisms and the risk of colorectal cancer

Rare germline variants in mismatch repair genes have been linked to hereditary nonpolyposis colorectal cancer; however, it is unknown whether common polymorphisms in these genes alter the risk of colorectal cancer. To examine the association between common variants in mismatch repair genes and colorectal cancer, we conducted a case-cohort study within the CLUE II cohort. Four single nucleotide polymorphisms in 3 mismatch repair genes (MSH3 R940Q, MSH3 T1036A, MSH6 G39E and MLH1 I219V) were genotyped in 237 colorectal cancer cases and a subcohort of 2,189 participants. Incidence rate ratios (RRs) and 95% confidence intervals (95% CIs) for each polymorphism were estimated. The MSH3 1036A variant was found to be associated with an increased risk of colorectal cancer (RR=1.28, 95% CI: 0.94-1.74 and RR=1.65, 95% CI: 1.01-2.70 for the AT and TT genotypes, respectively, with p(trend)=0.02), particularly proximal colon cancer. Although the MSH3 940Q variant was only weakly associated with colorectal cancer overall (p(trend)=0.07), it was associated with a significant increased risk of proximal colon cancer (RR=1.69, 95% CI: 1.10-2.61 and RR=2.68, 95% CI: 0.96-7.47 for the RQ and QQ genotypes, respectively with p(trend)=0.005). Processed meat intake appeared to modify the association between the MSH3 polymorphisms and colorectal cancer (p(interaction) < 0.10 for both). No association was observed with the MSH6 and MLH1 polymorphisms overall. This study suggests that common polymorphisms in the mismatch repair gene, MSH3, may increase the risk of colorectal cancer, especially proximal colon cancer.     

PARP Inhibitors and Prostate Cancer: To Infinity and Beyond BRCA

The U.S. Food and Drug Administration recently approved two poly‐adenosine diphosphate‐ribose polymerase (PARP) inhibitors, olaparib and rucaparib, for treatment of biomarker‐positive metastatic castrate resistant prostate cancer. The benefits of PARP inhibition have been well characterized in patients who have BRCA1 and BRCA2 mutations in several forms of cancer. BRCA1 and BRCA2 occupy key roles in DNA damage repair, which is comprised of several different pathways with numerous participants. Patients with mutations in other key genes within the DNA damage repair pathway may also respond to treatment with PARP inhibitors, and identification of these alterations could significantly increase the percentage of patients that may benefit from PARP inhibition. This review focuses on the potential for synthetically lethal interactions between PARP inhibitors and non‐BRCA DNA damage repair genes.Implications for PracticeThe treatment potential of PARP inhibition has been well characterized in patients with BRCA1 and BRCA2 mutations, but there is compelling evidence for expanding the use of PARP inhibitors to mutations of other non‐BRCA DNA damage repair (DDR) genes. This could increase the percentage of patients that may benefit from treatment with PARP inhibitors alone or in combination with other therapies. Understanding the significance of PARP inhibitor‐sensitizing alterations in other common non‐BRCA DDR genes will help guide clinical decisions to provide targeted treatment options to a wider population of patients.     

Immunotherapy of colorectal cancer: Challenges for therapeutic efficacy

A better knowledge of the complex interactions between cancer cells and the immune system has led to novel immunotherapy approaches. Treatment with selective anti-PD1, anti-PD-L1 and/or anti-CTLA-4 monoclonal antibodies (mAbs) has been a revolution in the therapeutic scenario of several cancer types, with the highest clinical efficacy in melanoma and in lung cancer. Colorectal cancer is one of the tumours in which immunotherapy has been shown less effective. Whereas in deficient mismatch repair (MMR) or in highly microsatellite instable (MSI-H) metastatic colorectal cancer there is clear clinical evidence for a therapeutic role of immune checkpoint inhibitors, the vast majority of patients with proficient MMR or with microsatellite stable (MSS) tumours do not benefit from immunotherapy. Defining the molecular mechanisms for immunogenicity in metastatic colorectal cancer is needed in order to develop predictive biomarkers and effective therapeutic combination strategies. A major challenge will be to identify, among the heterogeneous spectrum of this disease, those patients with specific tumour and tumour infiltrating stroma molecular and functional characteristics, that could be effectively treated with immunotherapy. In this review, we discuss the role of immune response in the context of metastatic colorectal cancer. We summarize the available clinical data with the use of anti PD-1/PD-L1 mAbs as single agents or in combination with anti CTLA-4 mAbs in MSI-H patients. Finally, we address the challenges and the potential strategies for rendering the more frequent microsatellite stable (MSS) tumours “immune-competent” and, therefore, amenable for effective immunotherapy interventions.     

Mismatch Repair Protein Defects and Microsatellite Instability in Malignant Pleural Mesothelioma

Introduction

Malignant pleural mesothelioma is an aggressive malignancy with limited systemic therapy options. Promising results have been reported with use of anti–programmed cell death 1 therapy; however, its benefits appear to be confined to a subgroup of patients. Microsatellite instability (MSI) results from the inactivation of DNA mismatch repair genes and results in a high tumor mutational burden, a phenomenon that has not been seen with mesothelioma. MSI and protein absence have been shown to correlate in colorectal cancer, such that most centers have adopted immunohistochemistry (IHC) to screen for MSI-high colorectal cancers. We profiled a large cohort of patients with mesothelioma to determine the rate of negative IHC staining results the four common mismatch repair proteins.

hMLHl and hMSH2 somatic inactivation mechanisms in sporadic colorectal cancer patients

Much is known about the role of germline inactivation in mismatch repair (MMR) genes in hereditary non-polyposis colorectal cancer (HNPCC), but the impact of somatic MMR gene changes on sporadic colorectal cancer remains to be elucidated. In hereditary cases the hMLHl and hMSH2 genes were shown to have a great importance, and in order to examine the somatic inactivation mechanisms of the two MMR genes hMLHl and hMSH2 we screened 37 Hungarian sporadic colorectal cancer patients for allelic imbalance (AI), microsatellite instability (MSI), hMLHl promoter hypermethylation and somatic mutations. Thirteen of the examined tumours (35%) were characterized by low-level MSI and none of the cases belonged to the high MSI group. Nine (24%) and seven (19%) cases had AI at the hMLHl and hMSH2 genes, respectively. Seven tumours (19%) showed dense promoter hypermethylation of hMLHl, but only two patients had somatic mutations, one for each MMR gene. According to our study on this limited set of cases the most prominent mismatch repair inactivation mechanism in sporadic colorectal cancer patients is the hMLHl promoter hypermethylation which may have a role in the carcinogenesis of sporadic colorectal cancer.     

Mismatch repair deficiency concordance between primary colorectal cancer and corresponding metastasis

Universal screening for mismatch repair deficiency (dMMR) in cancer is increasingly being implemented to detect Lynch syndrome and aid in treatment decisions. The mismatch repair (MMR) immunohistochemistry (IHC) concordance rate between primary colorectal cancer (CRC) and metastasis is unknown. At times, only metastatic tumor is available for screening (lymph node, liver, lung etc.) rather than the primary tumor. Therefore, it is important to confirm that tissue from metastases can be used for screening for dMMR. We tested dMMR primary and metastatic tumor to assess concordance between the two. We identified dMMR CRC resected at Ohio State University from 1999 to 2013 and stained a corresponding metastasis for all four MMR proteins (MLH1, MSH2, MSH6, PMS2) with IHC. A total of 50 primary CRC with dMMR and available regional lymph nodes (LN; 26 cases) or other metastatic tissue (24 cases) were identified. Thirteen cases were explained by MLH1 hypermethylation and 10 cases had Lynch syndrome. Two cases had somatic MMR mutations and the etiology for dMMR was unknown in 25 cases. All cases showed concordance in IHC staining between the primary tumor and corresponding metastatic tissue. In 36 cases, metastatic LN/other site was resected at the same time as the primary tumor. In 14 cases, time lapsed [median 16.5 months; quartile (Q)1 8.0; Q3 25; range 3–69] from the primary resection until metastatic resection. Metastatic tissue can be used to screen for Lynch syndrome and dMMR.     

Lack of involvement of nucleotide excision repair gene polymorphisms in colorectal cancer

DNA repair has an essential role in protecting the genome from damage by endogenous and environmental agents. Polymorphisms in DNA repair genes and differences in repair capacity between individuals have been widely documented. For colorectal cancer, the loss of mismatch repair gene activity is a key genetic determinant. Nucleotide excision repair (NER), recombination repair (RR) and base excision repair (BER) pathways have critical roles in protection against other cancers, and we wished to investigate their role in colorectal cancer. We have compared the frequency of polymorphisms in the NER genes, XPD, XPF, XPG, ERCC1; in the BER gene, XRCC1; and in the RR gene, XRCC3; in colorectal cancer patients and in a control group. No significant associations were found for any of the NER gene polymorphisms or for the XRCC1 polymorphism. The C allele (position 18067) of the XRCC3 gene was weakly but significantly associated with colorectal cancer (odds ratio 1.52, 95% confidence interval 1.04-2.22, P=0.03). For all patients who were heterozygous for any of the repair genes studied, tumour tissue was investigated for loss of heterozygosity (LOH). Only one example of LOH was found for all the genes examined. From the association and LOH data, we conclude that these genes do not have an important role in protection against colorectal carcinogenesis.     

Germline deletions in the <Emphasis Type="Italic">EPCAM</Emphasis> gene as a cause of Lynch syndrome – literature review

Lynch syndrome (clinically referred to as HNPCC – Hereditary Non-Polyposis Colorectal Cancer) is a frequent, autosomal, dominantly-inherited cancer predisposition syndrome caused by various germline alterations that affect DNA mismatch repair genes, mainly MLH1 and MSH2. Patients inheriting this predisposition are susceptible to colorectal, endometrial and other extracolonic tumors. It has recently been shown that germline deletions of the last few exons of the EPCAM gene are involved in the etiology of Lynch syndrome. Such constitutional mutations lead to subsequent epigenetic silencing of a neighbouring gene, here, MSH2, causing Lynch syndrome. Thus, deletions of the last few exons of EPCAM constitute a distinct class of mutations associated with HNPCC. Worldwide, several investigators have reported families with EPCAM 3’end deletions. The risk of colorectal cancer in carriers of EPCAM deletions is comparable to situations when patients are MSH2 mutation carriers, and is associated with high expression levels of EPCAM in colorectal cancer stem cells. A lower risk of endometrial cancer was also reported. Until now the standard diagnostic tests for Lynch syndrome have contained analyses such as immunohistochemistry and tests for microsatellite instability of mismatch repair genes. The identification of EPCAM deletions or larger EPCAM-MSH2 deletions should be included in routine mutation screening, as this has implications for cancer predisposition.     

Chemotherapeutic implications in microsatellite unstable colorectal cancer

Chemotherapy for colorectal cancer is currently offered to patients based on the stage of their cancer, and there is evidence to show an overall survival benefit with 5-fluorouracil-based (5-FU) therapy for patients with lymph node metastasis who receive it. The pathogenesis of colorectal cancer involves genomic instability, with about 15% of tumors demonstrating a form of genomic instability called high-frequency microsatellite instability (MSI-H) and due to loss of DNA mismatch repair function, and the remainder of colorectal tumors lacking MSI-H with retained DNA mismatch repair function and called microsatellite stable (MSS), with a large proportion of these tumors demonstrating another form of genomic instability called chromosomal instability. There is now evidence to show that the form of genomic instability that is present in a patient's colorectal cancer may predict a survival benefit from 5-FU. In particular, patients whose colorectal tumors have MSI-H do not gain a survival benefit with 5-FU as compared to patients with MSS tumors. In vitro evidence supports these findings, as MSI-H colon cancer cell lines are more resistant to 5-FU compared to MSS cell lines. More specifically, components of the DNA mismatch repair system have been shown to recognize and bind to 5-FU that becomes incorporated into DNA and which could be a trigger to induce cell death. The binding and subsequent cell death events would be absent in colorectal tumors with MSI-H, which have lost intact DNA mismatch repair function. These findings suggest that: (a) tumor cytotoxicity of 5-FU is mediated by DNA mechanisms in addition to well-known RNA mechanisms, and (b) patients whose tumors demonstrate MSI-H may not benefit from 5-FU therapy. Future studies should include a better understanding of the cellular mechanisms of the DNA recognition of 5-FU, multi-centered prospective trials investigating the survival benefit of 5-FU based on genomic instability, and the investigation of alternative chemotherapeutic regimens for patients with MSI-H tumors to improve survival.     

结直肠癌免疫检查点抑制剂治疗相关预测性标志物的研究进展

以免疫检查点抑制剂（immune checkpoint inhibitors,ICIs）为代表的免疫疗法开辟了肿瘤治疗的新纪元。目前ICIs已经广泛应用于晚期转移性结直肠癌患者的治疗。预测性标志物是精确筛选可从ICIs治疗中受益的患者群体的重要工具。本文回顾并总结了目前ICIs治疗结直肠癌重要的预测性标志物及其研究现状,包括错配修复缺陷及微卫星不稳定性、肿瘤突变负荷、DNA聚合酶ε/DNA聚合酶δ1以及PD-L1表达等。通过了解这些标志物对于结直肠癌ICIs治疗的响应及患者预后的预测价值,有助于指导临床医生筛选潜在获益人群,提高治疗效率,实现精准化治疗。     

A phase II trial of lomeguatrib and temozolomide in metastatic colorectal cancer

To evaluate the tumour response to lomeguatrib and temozolomide (TMZ) administered for 5 consecutive days every 4 weeks in patients with metastatic colorectal carcinoma. Patients with stage IV metastatic colorectal carcinoma received lomeguatrib (40 mg) and TMZ (50-200 mg m(-2)) orally for 5 consecutive days every 4 weeks. Response was determined every two cycles. Pharmacokinetics of lomeguatrib and TMZ as well as their pharmacodynamic effects in peripheral blood mononuclear cells (PBMC) were determined. Nineteen patients received 49 cycles of treatments. Despite consistent depletion of O(6)-methylguanine-DNA methyltransferase in PBMC, none of the patients responded to treatment. Three patients had stable disease, one for the duration of the study, and no fall in carcinoembryonic antigen was observed in any patient. Median time to progression was 50 days. The commonest adverse effects were gastrointestinal and haematological and these were comparable to those of TMZ when given alone. This combination of lomeguatrib and TMZ is not efficacious in metastatic colorectal cancer. If further studies are to be performed, emerging data suggest that higher daily doses of lomeguatrib and a dosing period beyond that of TMZ should be evaluated.     

Colorectal cancer intrinsic subtypes predict chemotherapy benefit,deficient mismatch repair and epithelial‐to‐mesenchymal transition

In most colorectal cancer (CRC) patients, outcome cannot be predicted because tumors with similar clinicopathological features can have differences in disease progression and treatment response. Therefore, a better understanding of the CRC biology is required to identify those patients who will benefit from chemotherapy and to find a more tailored therapy plan for other patients. Based on unsupervised classification of whole genome data from 188 stages I–IV CRC patients, a molecular classification was developed that consist of at least three major intrinsic subtypes (A‐, B‐ and C‐type). The subtypes were validated in 543 stages II and III patients and were associated with prognosis and benefit from chemotherapy. The heterogeneity of the intrinsic subtypes is largely based on three biological hallmarks of the tumor: epithelial‐to‐mesenchymal transition, deficiency in mismatch repair genes that result in high mutation frequency associated with microsatellite instability and cellular proliferation. A‐type tumors, observed in 22% of the patients, have the best prognosis, have frequent BRAF mutations and a deficient DNA mismatch repair system. C‐type patients (16%) have the worst outcome, a mesenchymal gene expression phenotype and show no benefit from adjuvant chemotherapy treatment. Both A‐type and B‐type tumors have a more proliferative and epithelial phenotype and B‐types benefit from adjuvant chemotherapy. B‐type tumors (62%) show a low overall mutation frequency consistent with the absence of DNA mismatch repair deficiency. Classification based on molecular subtypes made it possible to expand and improve CRC classification beyond standard molecular and immunohistochemical assessment and might help in the future to guide treatment in CRC patients.     

How Do We Make Choices in Salvage Therapy: Panitumumab, Cetuximab, or Regorafenib?

Colorectal cancer is the fourth commonest cancer worldwide. The survival rate is suboptimal for patients with metastatic disease. The introduction of anti-epidermal growth factor receptor (EGFR) antibodies has remarkably improved clinical outcomes. Two monoclonal antibodies targeting EGFR and one multikinase inhibitor have been approved by the FDA and Health Canada for the treatment of metastatic colorectal cancer; however, only about 10 % of patients respond to this treatment. Having wild-type KRAS is necessary but not sufficient to derive benefit from EGFR inhibition. Interestingly, patients with certain mutations such as p.G13D represent a cetuximab-sensitive subtype of KRAS mutant metastatic colorectal cancer. A few biomarkers have been identified, but we still do not know the best way to administer drugs. In this article we review the clinical data and expert opinions and summarize the recommendations.     

Antiangiogenic Drugs for Colorectal Cancer: Exploring New Possibilities

Angiogenesis is essential to cancer development and progression, and its inhibition has been shown to benefit patients with several different malignancies. A considerable number of antiangiogenic compounds have been evaluated for the treatment of colorectal cancer, but only bevacizumab and aflibercept were able to demonstrate a survival benefit in phase III trials. In this review, we discuss important aspects of the interrelationship between tumor cells and the microenvironment leading to tumor progression, with a focus on angiogenesis. Clinical data on antiangiogenic therapies for colorectal cancer in the metastatic and adjuvant settings, as well as the potential use of antiangiogenics beyond tumor progression are analyzed. The need to identify surrogate biomarkers towards a more personalized approach in oncology is emphasized as this is becoming increasingly important in drug development.     

The interaction of p53 and DNA repair gene mutations and their impact on tumor mutation burden and immune response in human malignancies

P53 suppresses tumorigenesis through multiple cellular functions/mechanisms, including genomic stability surveillance. Recently, it has also be reported for its role in cancer immune response modulation. Deficiency in DNA repair pathways lead to the accumulation of genomic alterations and tumor mutation burden and in consequence resulting in the activation of immune response. We investigated the interaction of p53 and DNA repair gene mutations and their impact on tumor mutation burden and immune response in human malignancies by mining cBioPortal data of a range of human cancers. We found that in the majority of human cancers, p53 mutations are equally distributed between DNA repair gene mutation positive and negative cases and in a number of human cancers, p53 and DNA repair gene mutations have a tendency of co-occurrence. Only in colorectal cancer, there is a tendency of ‘mutual exclusivity’ of mutations in p53 and DNA repair genes. In most tumors, p53 and DNA repair gene mutations have synergistic/additive effect in increasing tumor mutation burden, but not in colorectal cancer where they are mutually exclusive. The impact of p53 and DNA repair gene mutations and their interaction on tumor microenvironment immune cells are complex and tumor type specific and not always correlated with tumor mutation burden. In colorectal cancers, these two types of mutations resulted in similar immune cell subpopulation changes and in tumors where the mutations have a tendency of co-occurrence, p53 showed dominant roles on immune response, although they can also counter-act each other for their effect on certain immune cell subtypes.